Electrical Agents: Electrical Stimulation Techniques

1
Electrical AgentsElectrical Stimulation
Techniques

• Body Circuit
• As the of water in tissue increases, its
  ability to transmit electricity increases
• Tissues are either excitable (directly influenced
  by stimulation) or nonexcitable

2
Electrical AgentsCharacteristics of Electrical
Generators

• Excitable Tissue
• Nerve Fibers
• Muscle Fibers
• Blood Cells
• Cell Membranes
• Nonexcitable Tissue
• Bone
• Cartilage
• Tendons
• Ligaments

• Poor Conductor
• Skin
• Bone
• Tendons
• Fascia
• Adipose
• Good Conductor
• Muscle
• Nerve
• Blood

3
Electrical AgentsCharacteristics of Electrical
Generators

• The current enters the body through a series
  circuit since the skin is relatively consistent
• Once in the body it may take many different paths
• Current prefers the path of least resistance

4
Electrical AgentsElectrodes

• Placement of electrodes is important for athlete
  comfort and efficiency
• Electrodes can be of different materials
• In most cases a medium is needed to reduce
  resistance between the skin and the electrode
• Wet sponges
• Conducting gels

5
Electrical AgentsElectrodes

• Size of electrode inversely affects the density
  of the current
• Electrode size ? current density ?
• This affects comfort and effect of the current
• Larger electrodes produce greater contractions,
  but, not as specific

6
Electrical AgentsElectrodes

• Motor points, trigger points, acupuncture points
• Closer placement of electrodes vs. electrodes
  placed farther apart
• Closer superficial
• Farther deeper
• Direction of fibers is also important

7
Electrical AgentsElectrodes

• Bipolar Technique
• 2 leads, with equal size electrodes
• Monopolar Technique
• 1 or 2 active electrodes and a dispersive
  electrode
• Dispersive pad must be much larger than active
  electrodes

8
Electrical AgentsElectrodes

• Quadripolar Technique
• 2 sets of electrodes each from there own channels
• Current may intersect with each other

9
Electrical AgentsMovement of Electrical Current

• Most forms of electrical stimulation are applied
  transcutaneously
• When passed through the skin it has the potential
  to upset the resting potential of the axons
• Under the cathode depolarization occurs
• Under the anode hyperpolarization occurs

10
Electrical AgentsSelected Stimulation of Nerves

• Nerves response is based on 3 factors
• Relative diameter of the nerve
• larger stimulated first
• Depth of nerve in relation to electrode
• sensory are closer to surface than pain/motor
• Duration of the pulse
• shorter durations require more current to
  stimulate a nerve type

11
Electrical AgentsSelected Stimulation of Nerves

• Sensory nerves are stimulated first, then motor,
  then pain.
• Pain fibers are located in between sensory and
  motor fibers, but, are smaller in diameter

12
Electrical AgentsSelected Stimulation of Nerves

• Subsensory-level
• From zero intensity to point athlete first feels
  the current
• Sensory-level
• To point of slight muscle contraction
• Motor-level
• Visable contraction without pain
• Noxious-level
• Intensity that stimulates pain fibers

13
Electrical AgentsAccommodation and Habituation

• Accommodation
• Over time it will take more intensity to cause
  depolarization of the nerve
• Habituation
• CNS filters out a continuous, non-meaningful
  stimulus
• This can be seen when an athlete gets use to the
  current

14
Electrical AgentsMovement of Electrical Current

• Medical Galvanism
• Application of low voltage DC, with a known
  polarity under each electrode
• Certain cellular and biochemical responses occur
  due to each polarity
• Galvanic stimulation is the only form of current
  that can elicits a muscle contraction from
  denervated muscle, but the phase duration is so
  long it also activates the C fibers

15
Electrical AgentsMovement of Electrical Current

• Medical Galvanism (Cont.)
• Physiological effects are generally opposite
  under the cathode or anode
• Symmetrical or balanced currents can not have any
  galvanic effects
• Unbalanced asymmetrical current can result in
  residual chemical changes is current is high
  enough

16
Electrical AgentsElectrical Stimulation Goals
and Techniques

• Muscular Contractions
• Virtually any electric modality can achieve a
  contraction at a high enough intensity
• Contractions used to
• Retard effects of atrophy
• Reeducate muscle
• Reduce edema
• Electrodes should be placed over motor points

17
Electrical AgentsMuscle Contractions

• Muscular Contractions (cont.)
• Large nerve closer to electrode are recruited
  first
• If nerve is denervated, then DC or monophasic
  with a long pulse duration can be used to
  depolarize the motor unit

18
Electrical AgentsMuscle Contractions

• Pulse Amplitude
• As intensity increases so does the strength of
  the contraction
• Depth of penetration increases as the peak
  current increases, thus recruiting more nerve
  fibers
• Pain inhibits maximal contraction of fibers

19
Electrical AgentsMuscle Contractions

• Pulse Frequency
• Pulse rate of less than 15 pps twitch
  contraction
• Pulse rate between 15 and 40 pps summation of
  stimuli
• This will increase to the point of tetany
• Further increase in frequency will promote
  fatigue of the muscle

20
Electrical AgentsMuscle Contractions

• Pulse Frequency (cont.)
• Strong tetanic contraction is needed to delay
  atrophy
• Low pps decreases fatigue, but, produces less
  force
• High pps are more comfortable

21
Electrical AgentsMuscle Contractions

• Phase Duration
• To recruit motor units a moderate phase duration
  should be used
• 300 to 500 microseconds
• Strength Augmentation
• Voluntary contractions are better than
  electrically induced contractions

22
Electrical AgentsPain Control

• Reduce pain by assisting in the healing process
  or affecting pain transmission
• High pulse frequency, short duration, sensory
  level currents are thought to activate the gate
  control theory
• Low pulse frequency, long duration, high
  intensity and noxious stimuli are thought to
  stimulate release of opiates

23
Electrical AgentsPain Control

• During initial phases of pain control,
  electricity stimulates the dorsal horn of the
  spinal cord
• The placebo effect of electrotherapy can not be
  overlooked

24
Electrical AgentsCirculation

• Electrically induced contractions increase local
  blood flow the same as voluntary contractions
• Sensory level stimulation has not been found to
  effect blood flow

25
Electrical AgentsWound Healing

• Use of lower intensity DC may reduce the time
  needed for superficial wound healing by 1.5 to
  2.5 times
• Depending on the polarity, certain inflammatory
  mediators can be attracted or repelled from the
  area

26
Electrical AgentsWound Healing

• What occurs in the body
• Increased circulation
• Increased blood clot formation
• Antibacterial effects
• Influences on migration of cells
• Presence of an injury potential (theorized to
  electrically control tissue repair)

27
Electrical AgentsControl and Reduction of Edema

• Sensory-level stimulation
• Attempts to stop formation of edema by preventing
  the fluids, plasma proteins, and other solids
  from escaping into surrounding tissues
• Motor-level stimulation
• attempts to assist the venous and lymphatic
  system in returning the edema substances back to
  the torso

28
Electrical AgentsSensory-Level Stimulation for
Edema Control

• Used in acute trauma to attempt to decrease edema
  formation
• Intensity is kept below motor threshold
• Why does it work?
• Reduction in capillary pressure and capillary
  permeability
• Produces a vascular spasm and prevents fluid from
  leaking out of the vessels

29
Electrical AgentsMotor-Level Stimulation for
Edema Control

• Works by squeezing the vessels and milking the
  fluids out of the area
• Referred to as muscle milking or muscle pump
• Use 1 pps or tonic contraction with a 50 duty
  cycle
• Not as good as voluntary contractions
• If used limb should be elevated

30
Electrical AgentsFracture Healing

• Electricity has traditionally been used to heal
  nonunion fractures
• Current research is also looking into acute
  fractures
• Theory
• Bone cannot differentiate between the bodys
  innate charges need for normal bone growth and
  those from outside sources

31
Electrical AgentsFracture Healing

• Devices are known as bone growth generators
• Generally use AC for transcutaneous use and DC
  for implanted electrodes
• Usefulness is debatable
• Decrease in bone growth
• Time out due to surgical implant removal
• M.D. is the person who prescribes the unit

32
Electrical Agents

• General Contraindications
• Cardiac disability (Stimulation of thorax or neck
  may effect respiration or heart)
• Pacemakers
• Pregnancy
• Menstration

33
Electrical Agents

• General Contraindications (cont.)
• Cancerous lesions
• Sites of infections
• Exposed metal implants
• Severe obesity
• Epilepsy
• Electronic Monitoring Equipment

34
Electrical Agents

• Therapeutic Uses for Electricity
• Controlling acute and chronic pain
• Reducing edema
• Reducing muscle spasm
• Reducing joint contractures
• Inhibiting muscle spasm
• Minimizing disuse atrophy
• Facilitating tissue healing

35
Electrical Agents

• Therapeutic Uses (cont.)
• Facilitating muscle re-education
• Facilitating fracture healing
• Strengthening muscle